A car bomb explosion at a military base in the Colombian border city of Cucuta injured 36 people on Tuesday, the defense minister said, casting blame for the attack on leftist rebels.
The explosion took place at a base used by the 30th Army Brigade in the northeastern city near the border with Venezuela.
"We reject and repudiate this vile and terrorist act which sought to attack the soldiers of Colombia," Defence Minister Diego Molano told journalists. "Thirty-six people were injured. Three of them with a degree of gravity."
One of the injured has had surgery, Molano said, and 29 are hospitalized.
Two men drove a white Toyota truck into the base after passing themselves off as officials, he said, adding there were two explosions.
Despite a 2016 peace deal with Revolutionary Armed Forces of Colombia (FARC) rebels, Colombia's military continues to battle National Liberation Army (ELN) guerrillas, crime gangs and former FARC members who reject the accord.
The ELN, FARC dissidents and crime gangs are all present in sometimes-restive Norte de Santander province, where the 30th Brigade operates.
"The initial hypothesis is that the ELN are behind this demential and vile act," Molano said. "Also being investigated is the involvement of FARC dissidents."
The injury toll could have been higher but most personnel were in preventative isolation because of coronavirus, a high-ranking official told Reuters earlier on Tuesday.
Photos and video circulating on social media showed a destroyed white vehicle in flames.
President Ivan Duque said on Twitter he would travel to Cucuta to meet with military leaders and local authorities.
Social media videos showed what appeared to be U.S. military personnel on the base after the attack. Dozens of U.S. advisors are stationed in Colombia, but the U.S. military's Southern Command did not immediately respond to a request for comment.
The government blamed FARC dissidents for a car bomb attack in March in Cauca province which injured more than 40 people.
A 2019 ELN car bomb attack at Bogota's police academy killed 22 people and ended nascent peace talks between the group and the government.